Human Memory

It is good to have an end to journey towards; but it is the journey that matters, in the

end.Ursula K. Le Gui

Memory

• Process by which information is:– Acquired

• Encoding– Stored in the brain

• Storage– Later retrieved

• Retrieval– Eventually (possibly) forgotten

Information-Processing Model of Memory

• Computer as a model for our memory

• Three types of memory– Sensory memory– Short-term memory (STM)– Long-term memory (LTM)

• Can hold vast quantities of information for many years

Information-Processing Model of Memory

Short-termmemoryStimulus

Sensorymemory

Long-termmemory

Attention Encoding

Retrieval

Forgetting ForgettingForgetting

Sensory Memory

• Stores all the stimuli that register on the senses

• Lasts up to three seconds• Two types

– Iconic memory• Visual• Usually lasts about 0.3

seconds• Sperling’s tests (1960s)

– Echoic memory (we’ll come back to this)

Sensory

InputSensory Memory

Sperling’s Experiment• Presented matrix of letters

for 1/20 seconds– Report as many letters as

possible• Subjects recalled only half

of the letters• Was this because subjects

didn’t have enough time to view entire matrix? – No

• How did Sperling know this?

Sperling’s Iconic Memory Experiment

Sperling’s Iconic Memory Experiment

Sperling’s Iconic Memory Experiment

Sperling’s Iconic Memory Experiment

Sperling’s Experiment• Sounded low, medium

or high tone immediately after matrix disappeared– Tone signaled 1 row to

report– Recall was almost perfect

• Memory for images fades after 1/3 seconds or so, making report of entire display hard to do

High Medium

Low

Sensory Memory

• Echoic memory– Sensory memory for auditory input

that lasts only 2 to 3 seconds

• Why do we need sensory memory?

Short-term Memory

• Function– Conscious processing of information– Attention is the key

• Limits what info comes under the spotlight of short-term memory at any given time

• AKA working memory

Working orShort-term

Memory

Sensory

Input

Sensory Memory

Attention

Memorize the following list of numbers:

1 8 1 2 1 9 4 1 1 7 7 6 1 4 9 2 2 0 0 1

Write down the numbers in order.

Now, try again…

1812 1941 1776 1492 2001

Short-term Memory

• Limited capacity– Can hold 7 ± 2 items for about 20 seconds– Maintenance rehearsal

• The use of repetition to keep info in short-term memory

• CHUNK– Meaningful unit of information– Without rehearsal, we remember 4 ± 2 chunks– With rehearsal, we remember 7 ± 2 chunks– Ericsson & Chase (1982)

89319443492502157841668506120948888568772731418610546297480129497496592280

Long-term Memory

Working orShort-term

Memory

Sensory

Input

Sensory Memory

AttentionLong-term

memory

Retrieval

• Once information passes from sensory to short-term memory, it can be encoded into long-term memory

Encoding

Long-term memory - Encoding

• Elaborative rehearsal– A technique for transferring information into

long-term memory by thinking about it in a deeper way

• Levels of processing– Semantic is more effective than visual or

acoustic processing– Craik & Tulving (1975)

• Self-referent effect– By viewing new info as relevant to the self, we

consider that info more fully and are better able to recall it

Long-term memory

• Procedural (Implicit)– Memories of behaviors, skills, etc.

• Demonstrated through behavior• Declarative (Explicit)

– Memories of facts• Episodic – personal experiences tied to

places & time• Semantic – general knowledge

– Semantic network

Semantic Networks

Red

Fire

CherryRoses

Fire Engine

Apples

House

Green

Flowers

Daisies

Yellow

Orange

TruckBus

Ambulance

Sunrise

Sunsets Clouds

Retrieval

• Retrieval– Process that controls flow of information

from long-term to working memory store• Explicit memory

– The types of memory elicited through the conscious retrieval of recollections in response to direct questions

• Implicit memory– A nonconscious recollection of a prior

experience that is revealed indirectly, by its effects on performance

Retrieval – Explicit Memory

• Free-recall test– A type of explicit memory task in which a

person must reproduce information without the benefit of external cues

• Recognition task– A form of explicit memory retrieval in which

items are presented to a person who must determine if they were previously encountered

• Retrieval failure– Tip-of-the-tongue (Brown & McNeill)

Retrieval – Explicit Memory

• Context-Dependent Memory– We are more successful at retrieving

memories if we are in the same environment in which we stored them

• State-Dependent Memory– We are more successful at retrieving

memories if we are in the same mood as when we stored them

Retrieval – Implicit Memory

• Showing knowledge of something without recognizing that we know it

• Research with amnesics• Déjà vu

– The illusion that a new situation is familiar• Eyewitness testimony

– Eyewitness transference• Unintentional plagiarism

Forgetting

If we remembered everything, we should on most occasions be as ill off as if we remembered nothing.

William James• Lack of encoding

– Often, we don’t even encode the features necessary to ‘remember’ an object/event

• Decay– Memory traces erode with the passage of

time– No longer a valid theory of forgetting– Jenkins & Dallenbach (1924)

Interference theory

• Forgetting is a result of some memories interfering with others– Proactive interference

• Old memories interfere with ability to remember new memories

– Retroactive interference• New memories interfere with ability to

remember old memories– Interference is stronger when

material is similar

Forgetting• Repression

–There are times when we are unable to remember painful past events

–While there is no laboratory evidence for this, case studies suggest that memories can be repressed for a number of years andrecovered in therapy

Memory Construction

• Schema theory– Preconceptions about persons, objects, or

events that bias the way new information is interpreted and recalled

• Misinformation effect– The tendency to incorporate false postevent

information into one’s memory of the event itself

• Illusory memories– People sometimes create memories that are

completely false

Improving Memory

• Practice time– Distribute your studying over time

• Depth of processing– Spend ‘quality’ time studying

• Verbal mnemonics– Use rhyming or acronyms to reduce

the amount of info to be stored

Improving Memory

• Method of loci– Items to be recalled are mentally placed

in familiar locations• Interference

– Study right before sleeping & review all the material right before the exam

– Allocate an uninterrupted chunk of time to one course

• Context reinstatement– Try to study in the same environment &

mood in which you will be taking the exam